Wednesday, November 9, 2011 - 15:05
If your mailer has been an open relay for some time, and particularly if it has been used by spammers, it may well be on one or more blocklist.
The blocklist are a very important co-operative activity of the anti-spam community. Certain organisations or individuals maintain lists of IP addresses or address ranges and make them available in ways which enable users of the lists to reject attempted mail transfers from those addresses. Once your mailer is working properly you should check with all the lists you know and request removal if necessary.
